The present invention relates to an imaging system which utilizes a linear lens array in an optical system to transmit an image of a document at an object plane to an image plane at a reduction or enlargement value. More particularly, the invention relates to an imaging system which utilizes a moving document, a moving imaging assembly and a moving photoreceptor belt in a unique set of velocity relationships.
Document reproduction system utilizing linear lens array imaging ystems are known to the art in two principal embodiments. U.S. Pat. No. 3,544,190 is representative of these systems which utilize a linear stacked array of lenslets known as "strip lenses". U.S. Pat. No. 3,977,777 is representative of those scanning systems utilizing a scanning lens array comprising bundled gradient index optical fibers. Both of these imaging systems are desirable for use, for example, in document reproduction machines because they transmit an erect image to an imaging plane, have a short total conjugate and greatly reduce the mass and expense associated with the conventional lens, multi-mirror scan systems. Gradient index lens arrays have especially found wide acceptance as replacements for conventional image transmitting components in copiers as disclosed, for example, in U.S. Pat. Nos. 3,947,106 and 3,977,777. Each of these prior art copiers uses a single gradient index lens array to transmit images at a magnification of 1:1. And each of these imaging systems utilizes a fixed lens system, scanning being accomplished by moving the document past the lens in conjunction with a similar motion of a photoconductive imaging plane.
These systems, which can be characterized as moving platen or, more accurately, moving document systems, impose constraints on equipment size since the platen must travel the width of a document during the scan cycle.
Other scanning systems are known which accomplish the scanning function by moving a linear lens array beneath a fixed document. Illustrative of such systems are the scanning systems disclosed in U.S. Pat. No. 4,129,373 and Japanese Publication No. 55-1206.
A third system is known wherein the document, photoconductive imaging plane and linear lens array all move at speeds bearing a certain relationship to each other. This type of system, as disclosed in Japanese Publications 53-97436, 55-52074 and U.S. Pat. no. 3,754,822 have the desirable characteristics of compactness coupled with increases in copy rate for a given process speed.
All of the above-disclosed systems are related to imaging systems which transmit images at unity (1X) magnification. An imaging system using a linear lens array in a multi-magnification mode system is disclosed in copending U.S. Application No. 151,994, published as European Publication No. 0040548 on Nov. 25, 1981, assigned to the same assignee as the present invention. In this application various reproduction systems are disclosed which utilize a gradient index lens array as the imaging device. One embodiment disclose a lens assembly consisting of a 1X array coupled with a reduction/enlargement lens array, the latter constructed according to the principles disclosed in said application. This system utilizes a moving platen and fixed lens array, the platen to photoreceptor speed changing during magnification changes to maintain proper image exposure at the photoreceptor. The present invention is directed to modification of this sytem wherein the document, photoreceptor and lens array assembly are all moving in uniquely defined relationships during a reduction or enlargement mode of operation. More specifically, the invention is directed to an imaging system for projecting an erect image of a document lying in an object plane onto a photoreceptor lying in an image plane parallel to said object plane at at least one magnification m other than unity, said system including:
an imaging assembly positioned between said object plane and photoreceptor,
first drive means for driving said photoreceptor at a first velocity v,
second drive means for driving said document at a second velocity v', and
third drive means for driving said imaging assembly at a third velocity v", said first, second and third velocities being related by the expression ##EQU1##